body {
  overflow-x: hidden;
  -webkit-tap-highlight-color: transparent;
  -webkit-text-size-adjust: none;
  -moz-user-select: none;
  max-width: 540px;
  min-width: 320px;
  margin: 0 auto;
  background: #fafafc;
  font: 400 16px/1.5 PingFangSC-regular,Tahoma,"Lucida Grande",Verdana,"Microsoft Yahei",STXihei,hei;
}
a {
  text-decoration: none;
}
.search-index {
  display: flex;
  /* 固定定位的盒子与父级没有关系，它以屏幕为准 */
  position: fixed;
  top: 0;
  /* left: 0; */
  /* 让盒子居中 */
  /* left: 50%;
  transform: translateX(-50%); */
  /* 固定定位盒子必须要有宽度 */
  width: 100%;
  height: 44px;
  max-width: 540px;
  min-width: 320px;
  background-color: pink;
  /* 固定定位盒子来说，这个不起作用 */
  /* margin: 0 auto; */
}
.search {
  flex: 1;
}

.user {
  width: 44px;
  height: 44px;
  background-color: skyblue;
  font-size: 12px;
  text-align: center;
  color: #fff;
}

.user::before {
  content: '';
  display: block;
  width: 20px;
  height: 20px;
  background: url(../images/sprite.png) 0px 83px;
  background-size: 20px auto;
  margin: 5px auto 0;
}